This invention relates to the field of optical communication systems, more particularly to fiber-optic communications, especially distributed optical communication systems using dense wavelength division multiplexing.
Optical networks use modulated light to enable clear, rapid communication between two points. The bandwidth and efficiency provided by optical communication systems is well known. A single fiber is able to carry a great deal of information over a tremendous distance. Practical communication systems utilize large numbers of fibers networked together to form a communication web that provides at least one path between any two points on the network. Configuring the network to connect any two points requires a large number of switches.
One method of coupling optical fibers converts the optical signal carried by the input fiber to electrical signals and uses the electrical signal modulate another light beam that is transmitted along the second fiber. This method is much slower than simply switching the optical beam and may introduce noise into the transmitted optical signal. Purely optical switching, in which the optical beam from a first fiber is coupled directly to a second fiber without significant loss, is much faster and more efficient and is therefore desired.
Several types of optical switches have been developed. Some use mechanical means to physically align the input and output fibers. These mechanical switches typically are slow, large, and very expensive. What is needed is an improved optical switch that is very quick to configure and does not require the light beam to be converted to electricity.
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and system for an all-optical add drop multiplexer. One embodiment of the claimed invention provides an optical switch ideally configured for use as an optical add drop multiplexer. The optical comprises: a first input operable to provide a first input optical signal, a second input operable to provide a second input optical signal, a first output, operable to transmit either of the first and second signals, a second output operable to transmit the first signal; a retro-reflector, and a first, second, third, and fourth deflector. The first deflector is operable in a first state to direct the first input optical signal from the first input to a first point on the retro-reflector. The first deflector is operable in a second state to direct the first input optical signal to a second point on the retro-reflector. The second deflector is operable to direct the first input optical signal from the second point of the retro-reflector to the second output. The third deflector is operable to direct the second input optical signal from the second input to a third point on the retro-reflector. The fourth deflector is operable in a first state to direct the first optical input signal from the first point on the retro-reflector to the first output. The fourth deflector is operable in a second state to direct the second input optical signal from the third point on the retro-reflector to the first output.
A second embodiment of the present invention provides an optical switch ideally suited for use as an optical add drop multiplexer. The optical switch comprises: a first input operable to provide a first input optical signal, a second input operable to provide a second input optical signal; a first output, operable to transmit either of the first and second signals, a second output operable to transmit the first signal, a retro-reflector, a signal separator operable to receive the first input optical signal and to separate the first input optical signal into at least two first input signal components, and a first, second, third, and fourth deflector. The first deflector is operable in a first state to direct at least one the first input signal component from the first input to a first region of the retro-reflector. The first deflector is operable in a second state to direct at least one the first input signal component from the first input to a second region of the retro-reflector; The second deflector is operable to direct the at least one the first input signal component from the second region of the retro-reflector to the second output. The third deflector is operable to direct at least one component of the second input optical signal from the second input to a third region of the retro-reflector. The fourth deflector is operable in a first state to direct the at least one the first input signal component from the first region of the retro-reflector to the first output. The fourth deflector is operable in a second state to direct the second input optical signal from the third region of the retro-reflector to the first output.
Yet another embodiment of the present invention provides an optical switch ideally suited for use as an optical add drop multiplexer. The optical switch comprises: a first input operable to provide a first input optical signal, a second input operable to provide a second input optical signal, a first output operable to transmit either of the first and second signals, a second output operable to transmit the first signal, a first deflector, a second deflector, a third deflector, and a fourth deflector. The first deflector is operable in a first state to direct the first input optical signal from the first input to the fourth deflector. The first deflector is operable in a second state to direct the first input optical signal to the second deflector. The second deflector is operable to direct the first input optical signal from the first deflector to the second output. The third deflector is operable to direct the second input optical signal from the second input to the fourth deflector. The fourth deflector is operable in a first state to direct the first optical input signal from the first deflector to the first output. The fourth deflector is operable in a second state to direct the second input optical signal from the third deflector to the first output.
Still another embodiment of the present invention provides yet another optical switch ideally suited for use as an optical add drop multiplexer. The optical switch comprises: a first input operable to provide a first input optical signal, a second input operable to provide a second input optical signal, first output, operable to transmit either of the first and second signals, a second output operable to transmit the first signal, a signal separator operable to receive the first input optical signal and to separate the first input optical signal into at least two first input signal components, and a first, second, third, and fourth deflector. The first deflector is operable in a first state to direct at least one the first input signal component from the first input to the second deflector. The first deflector is operable in a second state to direct at least one the first input signal component from the first input to the fourth deflector. The second deflector is operable to direct the at least one the first input signal component from first deflector to the second output. The third deflector is operable to direct at least one component of the second input optical signal from the second input to the fourth deflector. The fourth deflector is operable in a first state to direct the at least one the first input signal component from the first deflector to the first output. The fourth deflector is operable in a second state to direct the second input optical signal from the third deflector to the first output.
The disclosed optical switch provides a low-cost, reliable, and optically efficient switch that does not require input signals to be converted from the optical domain to the electrical domain. Thus, the optical signals input to the switch are available as switch outputs without unnecessary signal delay or corruption.